Narrative:

This was a flight from tampa, fl, to cancun, mexico. When navigating on B646 from fish hook (fis) to robin intersection, the navigation is accurate only to vinka intersection. After that, fis takes you north of the airway, even though fis shows you still on course. This has been verified by cancun (cun) DME and havana center. Upon reaching the cun 011 degree radial, the cun DME is 122 mi, 36 mi north of course. All the time, fis shows us on course. At no time could we receive merida (mio), the other end of the airway. Also, starting about 150 mi out from fis, there is another station identifier on the frequency, making it difficult to hear the fis identify. The second identify sounded like w-z-M. This is the second trip I've made to cancun and I've had this problem both times. This is my second NASA report on the subject. Perhaps this route needs to be checked. Callback conversation with reporter revealed the following information: analyst and reporter discussed a normal error in reading butt end of needle flying out from ADF station as much as 200 mi. His company had not offered any information on variation error passing through 2 or 3 degrees of variation change. Reporter plans to discuss with his chief pilot.

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Original NASA ASRS Text

Title: FLC OF LGT NAVING BY ADF WAS ADVISED BY MUHA CENTER THEY WERE 15 MI N OF COURSE.

Narrative: THIS WAS A FLT FROM TAMPA, FL, TO CANCUN, MEXICO. WHEN NAVING ON B646 FROM FISH HOOK (FIS) TO ROBIN INTXN, THE NAV IS ACCURATE ONLY TO VINKA INTXN. AFTER THAT, FIS TAKES YOU N OF THE AIRWAY, EVEN THOUGH FIS SHOWS YOU STILL ON COURSE. THIS HAS BEEN VERIFIED BY CANCUN (CUN) DME AND HAVANA CENTER. UPON REACHING THE CUN 011 DEG RADIAL, THE CUN DME IS 122 MI, 36 MI N OF COURSE. ALL THE TIME, FIS SHOWS US ON COURSE. AT NO TIME COULD WE RECEIVE MERIDA (MIO), THE OTHER END OF THE AIRWAY. ALSO, STARTING ABOUT 150 MI OUT FROM FIS, THERE IS ANOTHER STATION IDENTIFIER ON THE FREQ, MAKING IT DIFFICULT TO HEAR THE FIS IDENT. THE SECOND IDENT SOUNDED LIKE W-Z-M. THIS IS THE SECOND TRIP I'VE MADE TO CANCUN AND I'VE HAD THIS PROBLEM BOTH TIMES. THIS IS MY SECOND NASA RPT ON THE SUBJECT. PERHAPS THIS RTE NEEDS TO BE CHKED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ANALYST AND RPTR DISCUSSED A NORMAL ERROR IN READING BUTT END OF NEEDLE FLYING OUT FROM ADF STATION AS MUCH AS 200 MI. HIS COMPANY HAD NOT OFFERED ANY INFO ON VARIATION ERROR PASSING THROUGH 2 OR 3 DEGS OF VARIATION CHANGE. RPTR PLANS TO DISCUSS WITH HIS CHIEF PLT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.